To elaborate, split db's involve linking to a back end file. When you create the links, you check the password option which doesn't "store" it in the fe in the sense of putting it in some table if that's what you meant. However, it's only invisible to the less knowledgeable, which might be good enough for your intention if that's to prevent casual snooping. If you need to take it up a step, then there's much more you'd need to do in which case you do want to follow the link and/or research it more. If you forget or lose this password you should consider yourself basically screwed unless you have a means of undoing the security barriers you've implemented. A backup of the fe that is not compiled (not an mde or accde file) and allows you to get at the nav pane might be enough.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.